Preliminary Study on Design of Longwall Mining from Final Highwall at Mae Moh Lignite Mine in Thailand

摘要

The EGAT Mae Moh lignite mine is the largest open-pit coal mine in Thailand. The total geological and economical reserves of Mae Moh coal field are approximately 1,140 Mt and 825 Mt, respectively. The annual production is 12 Mton, which represents 90 % of the total coal production in Thailand, and tends to decrease gradually. In this mine, the development of underground mine from final highwall is considered after the open-pit mining operation is finished. Longwall mining is one of the common methods for extracting coal in various thickness of coal seams and is much more effective, productive and safer than any other mining methods. The productivity of longwall mining is potentially high because it is basically a continuous operation requiring fewer workers and allowing a high production rate to be sustained. Due to unfavorable geological and geotechnical conditions such as weak strata and huge final pit slopes in this mine, however, various studies on the introduction of underground mining systems have been conducted so far. Optimizing boundary and/or safety pillars and panel design for both safety and economics is a key part of planning longwall mines. This paper discribes the applicability of the longwall mining system from final highwall and its suitable design taking the slope stability into consideration by means of three-dimensional explicit finite-difference program FLAC~(3D) producted by ITASCA.